1. Field of the Invention
The present invention relates to a pressure-sensitive adhesive (PSA) sheet with release liner comprising a release liner on a PSA layer (hereinafter, referred to as “release-lined PSA sheet”). In particular, it relates to a release-lined PSA sheet that is easy to handle when removing the release liner from the PSA sheet and adhering the sheet to an adherend and the release liner is highly recyclable. The present invention also relates to a release liner for a PSA sheet which is easy to handle and highly recyclable.
The present application is filed claiming the benefit of the priority based on Japanese Patent Application No. 2007-059468 filed on Mar. 9, 2007, the entirety of which is incorporated herein by reference.
2. Description of the Related Art
As a release liner for a PSA sheet, there has been known a release liner (release paper) formed of a paper substrate laminated with a polyethylene (PE) film. Recently, to facilitate air bubble elimination at time of PSA sheet attachment, there has been developed a release-lined PSA sheet in which the release liner has a structured surface so that the PSA layer is embossed with the corresponding structure. Related art of this type of technology is described in Japanese Patent Application Publication Nos. 2004-506777 and 2006-028416. As such a release liner with a structured surface, can be preferably used the aforementioned release liner formed of a paper substrate laminated with a PE film. For example, Japanese Patent Application Publication No. 2004-506777 (paragraph 0043) discloses an example of a release liner made of a paper substrate laminated with a PE coating on both sides.
A release-lined PSA sheet in which the release liner (can be simply referred to as “liner”) is constituted with a paper substrate having a PE layer on its surface is generally easy to handle because of the nature of the paper substrate. It is also advantageous because the performance is not likely to be affected by the operating temperature. However, a liner of such configuration lacks recyclability because the paper and the resin (PE) cannot be separated after use (that is, after it was removed from the PSA sheet). Moreover, a paper liner or a PSA sheet backed with the liner tends to be easily crinkled because of the surface roughness of the paper grain. This can cause unsightliness in the external appearance.
There has also been offered a no-paper liner. For example, Japanese Patent Application Publication 2004-506777, paragraph 0022, describes a liner of a polyethylene terephthalate (PET) coated (laminated) with PE having a silicone release coating, a liner of a cast polypropylene film having a silicone release coating, and the like.
Polyolefins such as PE is a resin of a different type from PET. Thus, in terms of improving the recyclability, a liner recyclable as a polyolefin material containing no other types of resin (such as PET) is desired.